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Thread: Level Flight Trim

  1. #1

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    Default Level Flight Trim

    After flying my aircraft for a few hours, I find that it requires a lot of forward stick just to maintain level flight. The top of the stick winds up about in line with the bottom of the instrument panel. This requires almost maximum extension of my arm, which is really uncomfortable. I've added a fixed elevator trim tab to relax the forward pressure, making it a little more bearable. With stick in this position, the elevator is 14 degrees down relative to the stabilizer. I would like to raise the leading edge of the stabilizer, to allow the elevator to fly more in trim.

    Is there any credible method of raising the stabilizer leading edge once the airplane is covered and assembled?

    The airplane flies like it's tail heavy, but the CG data does not bear that out.
    I've include the CG data:
    10.13 (10.6) fwd
    11.37 (16.0) aft
    (The parenthetical numbers are the limits.)

    If anything, the airplane is nose heavy according to the CG numbers.


    Thanks in advance,
    Chuck Gruby
    Petal, Kit Fox III Flying

  2. #2
    Senior Member
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    Default Re: Level Flight Trim

    Seems like a good time to check all your elevator rigging. That's the
    thought that jumps out at me.

    Jeff

    Quote Originally Posted by cgruby View Post
    After flying my aircraft for a few hours, I find that it requires a lot of forward stick just to maintain level flight. The top of the stick winds up about in line with the bottom of the instrument panel. This requires almost maximum extension of my arm, which is really uncomfortable. I've added a fixed elevator trim tab to relax the forward pressure, making it a little more bearable. With stick in this position, the elevator is 14 degrees down relative to the stabilizer. I would like to raise the leading edge of the stabilizer, to allow the elevator to fly more in trim.

    Is there any credible method of raising the stabilizer leading edge once the airplane is covered and assembled?

    The airplane flies like it's tail heavy, but the CG data does not bear that out.
    I've include the CG data:
    10.13 (10.6) fwd
    11.37 (16.0) aft
    (The parenthetical numbers are the limits.)

    If anything, the airplane is nose heavy according to the CG numbers.


    Thanks in advance,

  3. #3
    Senior Member
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    Nov 2008
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    KDKB (Dekalb, Illinois)
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    Default Re: Level Flight Trim

    Flaperon rigging, check that also

  4. #4
    Super Moderator Av8r3400's Avatar
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    Default Re: Level Flight Trim

    Quote Originally Posted by n85ae View Post
    Flaperon rigging, check that also


    X2 on the flapperon rigging.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  5. #5

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    Default Re: Level Flight Trim

    Flapperon rigging!!! I never thought of that. It's been checked several times after the rebuild job. But, I've never exercised the flapprons at all since I've had the plane. I guess I never saw a need for them, but I'll give it a try next flight.

    Thanks to everyone for you inputs.
    Chuck Gruby
    Petal, Kit Fox III Flying

  6. #6
    Super Moderator Av8r3400's Avatar
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    Default Re: Level Flight Trim

    If your flaps are reflexed up, this will give a nose up trim that will require pushing the stick forward.

    Try pulling on (back on the lever) some flap action and I'd bet this will solve your issue. Many of the early kitfoxes use the infinite flap adjustment as a pitch trim.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  7. #7
    Senior Member cap01's Avatar
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    Default Re: Level Flight Trim

    the forward stab mount bolt should have provisions for adjusting the leading edge of the stab up or down. at least the model IV does
    chuck
    kitfox IV 1050
    912ul warpdrive
    flying B , yelm, wa

  8. #8

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    Default Re: Level Flight Trim

    Quote Originally Posted by cap01 View Post
    the forward stab mount bolt should have provisions for adjusting the leading edge of the stab up or down. at least the model IV does
    Thanks a-heap, I'm going to try the flap trim first and see what the result of that is. I didn't see any additional holes in the stab mount, but they could be covered up with fabric.
    Chuck Gruby
    Petal, Kit Fox III Flying

  9. #9
    Senior Member cap01's Avatar
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    Default Re: Level Flight Trim

    If there is fabric on the stab attach bracket , you should check a little closer as there should be more holes . My IV is one of the really early ones and I'm pretty sure it has a III airframe .
    chuck
    kitfox IV 1050
    912ul warpdrive
    flying B , yelm, wa

  10. #10

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    Default Re: Level Flight Trim

    Quote Originally Posted by cap01 View Post
    If there is fabric on the stab attach bracket , you should check a little closer as there should be more holes . My IV is one of the really early ones and I'm pretty sure it has a III airframe .
    Thanks, at first look, I didn't see additional holes, but I'll check.
    Chuck Gruby
    Petal, Kit Fox III Flying

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